Low-energy flame thrower arrangement and a related method

ABSTRACT

A method for creating flames, wherein combustible powder material is injected into a gas stream ( 120 ) and the dispersed mixture of powder and gas is ignited and discharged through a nozzle ( 124 ). An arrangement suitable for implementing the method is also disclosed.

FIELD OF THE INVENTION

The invention relates to a method and arrangement for producing specialeffects such as low-energy flames.

BACKGROUND

Pyrotechnic effects producing large flames have been traditionallycreated by quickly burning large amounts of flammable liquid or gas. Forexample, explosion-like special effects may be achieved by dispersing acontainer filled with a flammable liquid with a small explosive charge.As a result the liquid is dispersed and ignited in the surrounding air,thereby creating a large fireball. A large special effect maycorrespondingly require very large amounts, e.g. tens or hundreds ofliters of flammable liquid.

Continuous large flames are typically generated by burning large volumesof some suitable flammable gas, e.g. butane or propane streaming out ofa nozzle. By varying the flow rate of the gas and the nozzle properties,flames of various sizes and shapes can be created.

Burning large volumes of flammable high-energy fuels such as gasoline orpropane causes significant safety risks as lots of heat is released inthe combustion process. This significantly limits the usability of suchmethods. For example, creating large flames indoors is very challengingand in many cases impossible because of the safety risks.

Some solutions have been developed for producing small flame effectsindoors, e.g. in theatres. These solutions are typically based onpyrotechnic compounds or burning e.g. black or smokeless gunpowder.These solutions are not completely risk-free as the smoke may be toxicand/or the compounds may explode in an uncontrollable manner. Inaddition, they require licenses and clearances to be used legally andare hazardous in storage and transport.

In prior art solutions using flammable liquids or gases, the flame maybe colored by e.g. adding color-donating salts into the liquid or gas.The resulting mixtures may develop toxic gases. For example, a greenflame may be achieved by adding barium chloride into the fuel, e.g.methanol. Additionally, some source of chlorine, e.g. hydrochloric acid,may be needed to make the color more vivid. Chlorinated materials maygenerate e.g. phosgene which is toxic even in small amounts.

Some power plants, e.g. those burning coal, are arranged to blow airinto the middle of a fuel cloud comprising of coal dust. As a result,the coal dust burns as quickly and efficiently as possible releasing asmuch energy as possible.

Publication JP2001132910 discloses a flame generator for achievingspecial effects. The generator consists of four nozzles that arearranged around an ignition device.

Publication JP7052114 discloses a fireworks device that is capable ofspreading the desired fireworks effect into a large area in acontrollable manner. The publication discloses the use of saw dust in afireworks device.

Publication US2270443 discloses a method and device for altering colorof a flame using some suitable powdered material. The flame in thisdisclosure is produced by burning some suitable gas as is generallyknown in prior art.

Publication U.S. Pat. No. 6,953,401 discloses a device for simulating aflame effect. The flame simulation is achieved by creating a wall of fogonto which a suitable beam of light is projected.

U.S. Pat. No. 5,756,920 discloses a flame cannon for producing anexplosion-like effect. The cannon includes a tank, a valve, a nozzle andan igniter. The tank is coupled to a carbon dioxide and a propanesource.

Thus, numerous techniques for producing large flames e.g. for specialeffect purposes are known in the art.

The objective of the present invention is to provide a method andarrangement for producing large low-energy flames by burning powderedmaterial(s), such as a powder comprising fine particles. Anotherobjective is to improve the safety of special effects with large flames.Yet another objective is to improve the controllability of specialeffect flames.

SUMMARY OF THE INVENTION

The present invention discloses a method and arrangement for producing alow-energy flame using powdered materials.

The method of the present invention is characterized in that combustiblepowder, e.g. some suitable powdered material is injected into a gasstream and the dispersed mixture of powder and gas is discharged througha nozzle and ignited.

The gas stream may comprise a core and an envelope component. The gasflow in the core component may be faster than the flow speed of theenvelope component. The gas flow in the core component mayadvantageously be at least slightly turbulent. Turbulence depends on theflow velocity. Especially when the flow velocity is low, a guidingstructure may be applied to adjust the turbulence so as to maintain theflame stable and/or prevent it from going out. The gas flow in theenvelope component may advantageously be laminar.

The nozzle may comprise at least one static or moving structure thatdivides the gas flow into the core component and the envelope componentsurrounding the core component.

The nozzle may comprise a component in which the diameter of the nozzlemay expand by 100%, 200%, 300% or 500% allowing the diameter of the gasstream to expand while flowing through the nozzle.

The nozzle may further comprise a cylindrical component.

The nozzle may be arranged to comprise or be attached to some suitablemeans for igniting the mixture of gas and powder. The means may includee.g. an ignition flame, electric spark or an electric heating element.The amount of energy used by the ignition means may be adjustable.

Preferably the utilized gas is relatively cold, e.g. below theautoignition temperature of the used fuel, and contains enough oxidantto burn a substantial portion of the powder and maintain the flame.

The gas advantageously contains oxygen. Suitably, the gas may be air.

The gas stream may be created using e.g. pressurized gas or a blower.The velocity of the gas stream may be adjusted to be suitable e.g. forthe powdered material and/or nozzle used.

The nozzle may comprise a means for generating turbulence in the gasstream. The turbulence may be advantageously generated such that itoccurs in the core component of the gas stream. Further advantageously,creation of turbulence is avoided in the envelope component of the gasstream.

The flow velocity of the gas stream at the nozzle exit may be e.g. atleast about 1, 10 or 20 m/s. At maximum, the flow rate of the gas streammay be e.g. up to about 20, 50 or 100 m/s or more. Preferably, the flowvelocity may be between about 5 and 20 m/s.

The feed rate of powder material into the mixing chamber and/or nozzlemay be e.g. at least about 20 g/s/m³, 200 g/s/m³, 2 kg/s/m³ or 20kg/s/m³ calculated to normal pressure.

The powder may be any suitable combustible powder, e.g. wood dust,potato flour, or wheat flour. It shall be noted that the heat ofcombustion of such powders are substantially lower than of conventionalfuels. In general, any finely divided, combustible organic or inorganicmaterial may be applicable as a powdered fuel.

The minimum particle size (diameter) of the powder may be e.g. about 1,5 or 10 micrometers. The maximum particle size of the powder may be e.g.about 20, 100, 500 or 1000 micrometers.

In some embodiments, a bimodal powder comprising a finely divided andcoarse grained component may be used.

The powder may comprise additional particles or bodies suitable forproducing additional effect in the flame. The additional effect may bee.g. a change of color of the flame or a pyrotechnic effect, e.g. anexplosion. Such additional effects may also be achievable by injecting,e.g. via an applicable injector, some suitable liquid into the gasstream. Examples of such materials are granulate or pellets or the likecomprising or consisting of a pyrotechnic composition, which igniteslater in the flame creating e.g. small explosion-like effects along thelength of the flame. The added particles may comprise easily ignitablemetal powders creating bright sparks in the flame and enhancing thevisual effect. The liquid may be a combustible or noncombustible liquid,which contains dissolved, color-enhancing materials coloring the flameto red, green, blue, lilac, violet, yellow or any other, desired colorexcept black. The particles, bodies or liquid added may also generatesmoke in the desired colors and/or they may produce any desired odournot normally obtained from burning fuels.

The fuel-to-gas ratio (kilograms of fuel/cubic meters of air calculatedto normal pressure) in the nozzle may be at maximum about 20 kg/m³, 10kg/m³ or 5 kg/m³.

and at minimum 2 kg/m³, 1 kg/m³1/g or 0.5 kg/m³, or even less, forexample. The suitable ratio depends e.g. on the powdered material usedand its moisture content as well as on the carrier gas used.

The components of the arrangement of the invention may be dimensionedand/or the feed rate of fuel and/or flow rate of gas may be adapted soas to produce a flame having a length of at least about 2, 3 or 4meters. Basically the flame may range from about 0.1 to over 10 meters.

The invention also concerns an arrangement that implements the methoddisclosed herein.

As to the utility of the present invention, the inventors havesurprisingly observed that the method and apparatus disclosed hereinallow controlled, relatively slow burning of powdered material thataccording to prior art would either burn explosively or not ignite atall. Inventors believe that the flow of gas as disclosed in variousembodiments of the invention contribute significantly to the phenomenon.The invention solves shortcomings of the prior art for example bycreating flames that emit relatively low amount of heat since they burnat an unusually slow rate for the material. The invention may be appliedto produce relatively large flames that can be safely used even byinexperienced operators and indoors. As a further benefit, fuel, whichis not classified as hazardous material, may be used.

Some embodiments of the invention are described herein, and furtherapplications and adaptations of the invention will be apparent to thoseof ordinary skill in the art.

BRIEF DESCRIPTION OF RELATED DRAWINGS

In the following, the invention is described in more detail withreference to the accompanying drawings in which

FIG. 1 a depicts an arrangement of an embodiment of the presentinvention,

FIG. 1 b is a combined block and flow diagram of an embodiment of thepresent invention,

FIG. 1 c is a flow diagram of an embodiment of the present invention,

FIG. 2 depicts an exemplary nozzle of an embodiment of the presentinvention,

FIG. 3 depicts an exemplary nozzle according to another embodiment ofthe present invention,

FIG. 4 a depicts a side view of an embodiment of the present invention,and

FIG. 4 b depicts a frontal view of the embodiment of FIG. 4.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 a illustrates a merely exemplary arrangement according to anembodiment of the present invention. The arrangement comprises a fuelsilo/hopper 100 that is connected to an injector 102 through a connector101. The connector 101 may comprise a means 105, such as a feeder, tocontrol the flow rate of the fuel powder (e.g. wood dust) from the fuelsilo 100 to the injector 102. A gas flow is provided by blowing gas(e.g. air) into the injector 102 through an air valve 104. In someembodiments, e.g. in those where the gas stream is provided by a fan,the air valve 104 may be optional. A dispersion of gas and fuel powderis lead from the injector 102 to the nozzle 103 in which it is ignitedby an ignition means (see e.g. FIG. 2 and related text) while beingblown out of the arrangement to form a preferably low-energy flame.Alternatively, an ignition means external to the nozzle 103 may beapplied. For example, the ignition means may be attached by a stand tothe outer surface of the nozzle or other element of the arrangement andbe aligned so as to enable igniting the dispersion exiting the nozzle103.

FIG. 1 b illustrates a combined block and flow diagram of an embodimentof the present invention. Broken arrows indicate gas flow, a thin arrowindicates the flow of fuel powder, thick arrows indicate the flow ofgas/fuel dispersion, and a hollow arrow indicates the emission a flame.Fuel storage 100 b such as the aforesaid silo is utilized for providingthe fuel powder into a feeder/mixer block 102 b wherein it is mixed withthe gas provided thereto e.g. by a compressor or other feasible gasstream creation element 104 b and optionally an intermediate transportpipe 106. Subsequently, the dispersion is conveyed to thenozzle/ignition block 103 b, optionally via another transport pipe 108.Control logic and optional safety circuit(s) 110 may be applied incontrolling and monitoring the operation of various elements of thearrangement as indicated in the figure by the connecting lines. Thelogic 110 may include a microprocessor, a microcontroller, aprogrammable logic chip, an ASIC, etc. in addition to various datastorage means such as a RAM/ROM memory chip. Power systems 112 maysupply power to one or more elements by a battery, for instance.

FIG. 1 c discloses a flow diagram of a basic embodiment of a method inaccordance with the present invention. Such method may be executed by anarrangement according to the present invention, such as the arrangementof FIG. 1 a or 1 b. At 120 the fuel powder is mixed with gas asdescribed hereinbefore. Then the obtained dispersion is optionallyadjusted as desired. For example, the stream may be divided into coreand envelope components, and turbulence may be introduced thereto. At124 the mixture is ignited and discharged through the nozzle, the actualtemporal order of these actions being dependent on e.g. whether theignition means is integrated in the nozzle (i.e. substantiallysimultaneous ignition and discharge) or implemented as a separateelement (discharged first). A skilled person will appreciate the factthat the presented method may be supplemented with various additionalphases and operations in view of the teachings provided herein.

FIG. 2 illustrates a nozzle 200 (corresponding to e.g. nozzle 103 ofFIG. 1) of an embodiment of the present invention in more detail. Thenozzle 200 is attached to a connector 201 through which the gas streamis flowing. In one embodiment, the length of the nozzle is about 150millimeters and the outer diameter is about 50 mm. The connector 201 hasa length of about 30 mm and inner diameter of about 15 mm. Inside thenozzle, there may be one or more structures or other arrangements 202,203 to divide the gas stream into core and envelope components andoptionally to cause suitable turbulence in the core component of thestream before the dispersed mixture is ignited using an ignition means204.

FIG. 3 illustrates a nozzle 300 of another embodiment of the presentinvention depicted in two side view projections. The nozzle comprises aconical section 301 and a cylindrical section 302. A structure assembledfrom perforated steel band (303-305) is attached to the cylindricalsection. The width of the perforated steel band (e.g. “Patent Band”) maybe e.g. about 1-2 cm. The structure comprises a connection means 303that connects the structure to the cylinder section 302. The guidingstructure 304 divides the gas flow into core component and envelopecomponent. The structure 305 causes slight turbulence to the corecomponent of the gas stream consisting of mixture of gas and powder,e.g. wood dust, potato flour or wheat flour in air.

Various features of the afore-explained embodiments relating to nozzles200, 300 may also be modified and/or combined by a skilled person.

In the following, few test results of using an embodiment described inFIGS. 1 and 2 are provided. A butane torch (100 g/h) was used forigniting the mixture of fuel and air. A compressor capable ofcompressing air to pressure of up to 6 bar and a 20 liter tank were usedas the source of air. Surprisingly, positive pressure of less than 1 bargauge was needed in the tests. The inventors thus became convinced thatsuitable gas stream may also be achievable with a low-pressure blower,e.g. the one utilized in a common household vacuum cleaner.

When operating the arrangement described in FIGS. 1 and 2 using wooddust as fuel and fuel-to-air ratio of about 6 kg/m³, the arrangementproduced a horizontally oriented flame of about 7 meters length.

In the tests, the flame was burning for about 7-8 seconds, on average.Some test runs tried to maximize the burning time of the flame on sameamount of fuel. In these test runs, the burning times were between about10-12 seconds. At all times the flame died when the fuel ran out. Hence,it is evident that unlimited fuel and air supply would lead to anunlimited time of controlled burn.

When operating the arrangement using wood dust (moisture content about4.3%) and fuel-to-air ratio of about 3 kg/m³, the arrangement produced ahorizontally oriented flame of about 3.8 meters length.

When operating the arrangement using wheat flour (moisture content about10%) and fuel-to-air ratio of about 10 kg/m³, the arrangement produced ahorizontally oriented flame of about 3 meters length.

FIG. 4 a depicts a side view of an embodiment of the present invention.The arrangement comprises a fuel intake 400, a feeder 405, such as arotary feeder, an air intake 404 comprising e.g. a blower, a mixer 402,a nozzle 403, a feeder motor 405 b, one or more pressure sensors 410 anda sensor air pipe 412 related thereto for precise control of theoperational parameters (DATA refers to a pressure signal). An ignitionmeans may be integrated, optionally removably, with the nozzle 403(built-in, for example) or be external thereto.

FIG. 4 b depicts a frontal view of the same embodiment wherein onepossible implementation of a rotary feeder 405 c is shown in more detail(rotor shaft with vanes) on the left. Advantageously the overallconstruction of the arrangement is modular in a sense that variouselements thereof are separable parts including the feeder 405, the airintake 404, the mixer 402, and/or the nozzle 403, for instance.Modularity enables changing individual elements to better fit eachpotential use scenario or upon a failure.

As shown in the above examples, the embodiments of the present inventionfacilitate burning a powder comprising fine particles in a controllablemanner. As only a relatively low amount of relatively low-energy fuel isneeded to generate a large flame, the amount of energy (heat) releasedby the combustion is quite low. The controllability of the flame hasbeen observed to be quite easy e.g. by controlling the feed rate of gas(air) and/or fuel. For example, changes in the fuel feed rate arepractically immediately observable in the flame. Another advantage ofthe embodiments of the present invention is that, unlike the fuels ofprior art solutions, the fuel usable in the various embodiments of theinvention is safe to store, transport, handle and use. Typically, nopermissions and/or special skills or caution is required when dealingwith the fuel. Furthermore, the fuel usable in the embodiments of theinvention is typically not classified as a hazardous material.

The scope of the invention can be found in the following claims.Notwithstanding the various embodiments described hereinbefore indetail, a person skilled in the art will understand that differentmodifications may be introduced to the explicitly disclosed solutionswithout diverging from the fulcrum of the present invention as set forthin this text and defined by the independent claims. For example,selected features of different embodiments may be cleverly combined tocome up with a new embodiment with desired properties.

1-15. (canceled)
 16. A method for creating flames by a flame-throwerarrangement, characterized in that combustible powder material isinjected into a gas stream (120) and the dispersed mixture of powder andgas is discharged through a nozzle, ignited, and blown out of thearrangement (124) so as to create a flame.
 17. A method according toclaim 16, wherein said gas stream is divided into core and envelopecomponents (122).
 18. A method according to claim 16, wherein turbulenceis formed in the core component of said gas stream comprising core andenvelope components, wherein the gas flow in the envelope component isoptionally laminar.
 19. A method according to claim 16, wherein said gasstream is created by at least one element selected from the groupconsisting of: pressurized gas, blower and chemical gas generator.
 20. Amethod according to claim, 16 wherein said powder material comprises atleast one element selected from the group consisting of: wood dust,potato flour, and wheat flour.
 21. A method according to claim 16,wherein the powder material further comprises additional particles orbodies for changing the color of the flame, producing odour or creatinga pyrotechnic effect, such as an explosion or smoke.
 22. A methodaccording to claim 16, wherein predetermined liquid is further injectedinto the gas stream for changing the color of the flame, producing odouror creating a pyrotechnic effect, such as an explosion or smoke.
 23. Amethod according to claim 16, wherein said mixture is ignited in thenozzle.
 24. A method according to claim 16, wherein fuel-to-gas ratio insaid nozzle is at maximum about 20 kg/m³ and at minimum about 0.02kg/m³.
 25. An arrangement for creating flames, characterized in that thearrangement comprises a means (102, 102 b) for injecting combustiblepowder material into a gas stream, a means for discharging the dispersedmixture of powder and gas through a nozzle (103, 103 b, 108, 200, 300),and a means for igniting (103 b, 204) the mixture blown out of thearrangement so as to create a flame.
 26. An arrangement according toclaim 25, wherein the arrangement further comprises a means (304) fordividing said gas stream into core and envelope components.
 27. Anarrangement according to claim 26, wherein the arrangement comprises ameans (305) for forming turbulence in said core component of said gasstream.
 28. An arrangement according to claim 25, wherein said means forigniting (103 b, 204) are integrated with the nozzle (103, 103 b, 200,300).
 29. An arrangement according to claim 25, wherein it furthercomprises a means for injecting liquid into the gas stream in order tochange the color of the flame, produce odour or create a pyrotechniceffect, such as an explosion or smoke.
 30. A flame-thrower for creatingvisual effects by flames, characterized in that it comprises thearrangement of claim
 25. 31. A method according to claim 17, whereinturbulence is formed in the core component of said gas stream comprisingcore and envelope components, wherein the gas flow in the envelopecomponent is optionally laminar.